Tension control system for converting packages of elastic thread

ABSTRACT

A system and method for tension control in a thread feeding system that provides a fast and reliable method for feeding elastomeric thread or fiber from a package to a thread processing system. The system includes a driven elastomeric thread package holder. The thread feeding system also includes a variable-speed motor configured to drive the driven elastomeric thread package holder.

BACKGROUND

One common method of unwinding thread from a cylindrical mandrel (or “package”) in a manufacturing process is referred to as over end takeoff (OETO). It should be noted that the terms “thread” or “fiber” are used interchangeably throughout this document. One issue common with OETO is unacceptable variations in threadline tension. These variations in threadline tension may result in excess utilization of thread, breakage of the thread in the manufacturing process, or poor product quality. Further, most thread vendors' product OETO thread packages by rewinding an as spun roll. This step incurs additional processing and cost.

Another common method of unwinding thread from a cylindrical mandrel (or “package”) in manufacturing processes is referred to as “rolling takeoff” which works in a draft mode or draw. This method also may include unacceptable variations in threadline tension resulting in many of the same issues described above.

The aforementioned problems make the processing of elastomeric threads problematic. Furthermore some applications (e.g., manufacturing of diapers and other personal care products) require the use of as-spun thread or fiber that is substantially finish-free. Therefore, a fast and reliable method of unwinding and feeding elastomeric thread from a package to a thread processing system is still needed in the art.

SUMMARY OF THE INVENTION

The present invention is a system, apparatus and method for tension control in a thread feeding system that provides a fast and reliable method for feeding elastomeric thread or fiber from a package to a thread processing system. One version of the present invention includes a thread feeding system including guide rolls configured to guide an elastomeric thread through a thread path of the thread feeding system and a driven elastomeric thread package holder. The thread feeding system also includes a variable-speed motor configured to drive the driven elastomeric thread package holder and a first-tension sensor configured to determine the tension on the thread. The thread feeding system also includes a first tension controller device configured to control a speed of the variable-speed motor.

Another version of the present invention includes a method for controlling elastomeric thread tension in a thread feeding system for a manufacturing system. The method includes measuring a thread tension of a moving elastomeric thread and determining whether the moving thread has a tension that is out of range relative to a predetermined tension value. The method also includes controlling the speed of a driven elastomeric thread package holder and delivering the thread to a desired location in the manufacturing system.

Finally, another version of the present invention includes a thread feeding system including guide rolls configured to guide an elastomeric thread through a thread path of the thread feeding system. The system also includes a driven elastomeric thread package holder and a variable-speed motor configured to drive the driven elastomeric thread package holder. The system includes at least one guide located less than 0.5 meter from the driven package holder; a first tension sensor configured to determine the tension on the thread; and a first tension controller device configured to control a speed of the variable-speed motor. Further, the speed of the variable-speed motor is adjusted to maintain the tension on the thread within a predetermined range of thread tension values.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and aspects of the present invention and the manner of attaining them will become more apparent, and the invention itself will be better understood by reference to the following description, appended claims and accompanying drawings, where:

FIG. 1 illustrates a plan view of an embodiment of a thread feeding system; and

FIG. 2 illustrates a plan view of a second embodiment of a thread feeding system which feeds multiple threads.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a thread feeding system (40). As shown in FIG. 1, a package (10) is held by a driven elastomeric thread package holder (12). The package holder (12) is sized such that the package (10) may be placed on the holder (12). The package holder may be adapted to contact a core of an elastomeric thread package. Alternatively, the package holder may be adapted to contact the circumference of the elastomeric thread package. The thread or fiber (11) is then directed, in sequence, through a static guide (14) having a substantially circular orifice; a tension device (16) around which the fiber may be wrapped; and a driven take-up roll or set of rolls (18). The static guide (14) is typically an orifice whose inner surface can be a highly polished ceramic material. Such a surface can provide excellent wear resistance and low friction. The take-up roll or rolls (18) representing that part of the manufacturing process equipment to which the thread or fiber is being supplied, is/are rotated at a speed relatively higher than the elastomeric thread package holder (12), so as to provide the desired draft.

The package holder (12) is connected to a variable-speed motor (24). A distance (d) between the package and the first static guide (14) may be relatively short, such as less than 1.00 meter, or less than 0.50 meter or less than 0.25 meter. These short distances may allow for compact thread feeding systems (40). During run, the thread is removed from the package (10) and the driven holder speeds up or slows down depending on the tension measured by the tension device (16) and a predetermined range of thread tension values. One or more additional guides (20), (22) for stabilizing the position of the threadline may be provided along the threadline.

The following paragraphs give exemplary details of the operation of the drive and tension control apparatus in terms of guides (20), (22), tension sensor (16), motion sensor (26), and break sensor (28).

The thread feeding system (40) may be attached to a central frame member to form a free standing process. Alternatively, the feeding system may be integrated into a manufacturing system such as an absorbent article manufacturing system.

Alternatively one or more portions of the feeding system (40) may be integrated into the manufacturing system while other portions remain free standing.

As illustrated in FIG. 1, a driven elastomeric thread package holder (12) holds a package (10) and rotates thereby feeding the thread off the package. After the thread comes off the package (10), the thread may be directed by static guides (14). If multiple threads are being used, a static guide (14) may be provided for each thread. Alternatively, if two packages (10) are held by one package holder (12), the two strands may pass through a single static guide (14), thereby treating the two or more strands as a single strand. Static guide (14) is preferably an orifice through which the thread passes. The static guides (14) may be substantially circular orifices. However, static guides (14) are not limited to having a circular orifice for directing the thread. As can be appreciated, alternative embodiments may use any known or appropriate guide device for directing the thread.

Thread feeding system (40) includes a driven package holder (12) and a tension control device (30) that is used to increment, maintain or decrease the amount of tension in the elastomeric thread. The tension controller (30) is connected to a tension sensor (16). The tension sensor (16) determines a measure of the tension of the thread as the thread comes off the driven package holder (12) and generates a signal representative of that tension.

The tension sensor (16) is positioned after the driven package holder (12) and in the thread path. The distance the thread travels between the driven package holder (12) and tension sensor (16) is preferably minimized. Reducing the distance the thread travels between driven package holder (12) and tension sensor (16) enables the thread feeding system (40) to better account for tension variations occurring at the point where the correction is being made (i.e., at the driven package holder (12)). A substantial distance between driven package holder (12) and tension sensor (16) may add additional tension variations not seen at the driven package holder (12).

As shown in FIG. 1, guides (14), (20) and (22) may include a combination of static guides and captive rolling guides which direct the thread through the feeding system (40). Alternatively, any of the guides (14), (20), (22) may be eliminated from the feeding system (40) if an applications performance can be improved through the use of fewer guide rolls.

After the thread passes through the static guides (14) the thread engages a guide roll (20) configured to direct the thread through the thread feeding system (40). Again, if multiple threads are being used, a guide roll (20) may be provided for each thread. If the thread feeding system (40) is supplying multiple thread groups to the manufacturing system, multiple thread feeding systems (40) may be added as shown in FIG. 2.

Multiple tension sensors (16, 16′) may be used to determine a net tension value for a group of threads. Multiple break sensors (28, 28′) may be used to determine whether there is a break in any individual thread or fiber. In addition, multiple motion sensors (26, 26′) may be added to determine whether individual threads are moving. Non-limiting examples of tension, breakage and motion sensors are also available from BTSR.

The tension sensor (16) may be attached to a tension controller device (30) which may be a programmable device that implements a tension trimming algorithm in accordance to programs and parameters entered into the device. A non-limiting example of such a tension controller device (30) is a Cygnus Digital tension controller manufactured by Magnetic Power Systems, Inc., 1626 Manufacturers Drive, Fenton, Mo. Another suitable tension controller device (30) is available from Dover Flexo Electronics, Inc., 217 Pickering Road, Rochester, Minn. The tension controller (30) may include, but is not limited to a digital display or readout (32) that provides information on the controller operation and measurements; input devices (34) such as buttons, keyboard, or a touch panel for inputting information, and indicator lights (36); such as light-emitting diodes, that represent the status of the device and alarms.

FIG. 1 shows the motor (24) for the driven package holder (12) and the connection between the motor (24) and the tension controller device (30). Cable (38) may be used to make the electrical connection for the control signals transmitted between the tension controller device (30) and the variable speed motor (24). A variety of electrical interfaces including but not limited to, serial bus, parallel bus, PMCIA bus and USB bus interfaces may be transmitted using cable (38). Signals from the tension controller device (30) are used to control the speed of the variable speed motor (24).

The variable-speed motor (24) may include a drive shaft attached to a package holder (12). The motor (24) is a variable speed motor. This is in contrast to the constant speed motors typically used in background art unwinding devices/thread feeding systems. The thread feeding system, including the tension controller device (30) provided after driven package holder (12), monitors the tension of the thread coming off the driven package holder (12) and alters the speed of motor (24) to control the tension of the thread (11).

Variable-speed motor drive systems are well known, as are the corresponding control systems. It should be understood that the thread speed in the present invention may be driven and controlled by any suitable or otherwise appropriate drive and control system. The variable speed motor (24) may be a servomotor and the tension controller device (30) may be a servo driver having a built in PID controller. One vendor providing such controllers is Emerson Control Techniques, 12005 Technology Drive, Eden Prairie, Minn. 55344. A non-limiting example of such a variable speed motor is the Emerson Control Techniques Unimotor Series, Model 75EZB301CACM, which may use an Emerson Control Techniques Undrive Series, Model SP1201, Drive Controller. This variable speed motor drive system includes an internal tension PID so that an external PLC or other motor controller is not required. The system has an approximate update time of 250 microsecond (μs) on the tension input. Another example of such a system is an Allen-Bradley ControlLogix controller, SERCOS interface module, Allen-Bradley servo drives and MPL-A310F motor.

In one embodiment, tension sensor (16) is a strain gauge load cell sensor that provides an output voltage signal to tension controller device (30) that is representative of thread tension. One suitable strain gage sensor is a MagPower CL1-5 or LC-5000 tension sensor (16) available from Magnetic Power Systems, Inc., 1626 Manufacturers Drive, Fenton, Mo. As can be appreciated, the thread feeding system (40) may include any sensor suitable to provide an output signal representative of thread tension. As yet another alternative, a displacement LVDT load cell type sensor may also be used.

Tension sensor (16) may be calibrated to have a tension detection range between 0 grams and 500 grams. Alternatively, tension sensor (16) may be calibrated to have a range of detection between 0 grams and 1000 grams. As can be appreciated, tension sensor (16) may be calibrated to have a variety of ranges of tension detection depending on the application. In addition, alternative embodiments may utilize additional tension sensors variously located throughout the thread feeding system. However, as can be appreciated, these tension sensors may include a variety of characteristics and calibrations.

The tension sensor (16) may utilize a variety of voltage, current, magnetic or other representative signals and a variety of ranges for these representative signals. More specifically, the tension sensor (16) may supplies an output signal in the form of a voltage to the tension controller device (30) that is dependent on the thread tension. Tension sensor (16) may provide an output voltage signal ranging from 0 volts to 10 volts that is representative of thread tension.

Guide rolls (42), (44) and tension sensor (16) define a wrap angle (θ) in the range of 5 to 210 degrees of circumference for the thread around the tension sensor (16). Preferably, the thread is wrapped over the range of 45 degrees to 190 degrees. Directing the thread through tension sensor (16) at the wrap angle (θ) enables the tension sensor (16) to more easily be calibrated based on the type of thread and the number of threads being used. A predetermined wrap angle (θ), at a predetermined tension, will provide a resultant force on the tension sensor (16).

This resultant force is detected by tension sensor (16) and converted into an output signal that can be recognized by tension controller device (30).

In one embodiment, a user enters directly into tension controller device (30) a desired tension setpoint that is to be maintained for the thread. The tension controller device (30) receives input signals from the tension sensor (16) representative of the thread tension. Tension controller device (30) uses these input signals to determine whether the tension level of the thread coming off driven package holder (12) can be maintained because it is at set point, or whether the tension needs to be increased or decreased.

The tension controller device (30) will change the speed of the variable speed motor (24) in order to minimize the difference between the thread tension and the set point.

If the tension controller device (30) determines that the thread tension after the driven package holder (12) is too high, the tension controller device (30) will increase the speed of motor (24). Alternatively, if the tension controller device (30) determines that the thread tension (12) is too low, the tension controller device (30) will decrease the speed of motor (24).

As described above, thread feeding system (40) may be configured to look at a signal from the tension sensor (16) in determining the appropriate speed for motor (24). Further, thread feeding system (40) may include multiple sensors positioned throughout the system that determine the appropriate speed of motor (24).

In the configuration shown in FIG. 1, the control of the speed of motor (24) may be is based solely on tension feedback from an individual tension sensor (16). In this case, the changes in speed may likely occur frequently and in large increments/decrements. An advantage that the present system utilizing a driven package holder (12) may have over systems utilizing OETO is that large decrements in the speed of the motor (12) will not cause slack in the thread (11). In the OETO system, a large decrement in the speed of a motor may cause slack in the thread which may lead to subsequent slippage or tangling, and therefore breakage of the thread. This characteristic of the present system may eliminate the need for any pretensioners in the system.

FIG. 2 illustrates a thread feeding system (40) designed to feed a plurality of threads, specifically two threads (11), (11′), into the manufacturing system. Specifically, FIG. 2 illustrates a plurality of driven package holders (12), (12′) and a plurality of tension sensors (16), (16′). In FIG. 2 element numbers followed by a prime (′) indicate duplicative elements. Duplicative elements, such as motor (12) and motor (12′) may be identical; alternatively, duplicative element may be substantially similar. Tension controller devices (30) and (30′) may be programmed separately, such that they independently control threads (11) and (11′). Alternatively, tension controller devices (30) and (30′) may include additional programming such that the two devices control the tension of threads (11) and (11′) together. For example, the controller devices may control the tension of each individual thread within range X, and control the combined tension of the thread within a second range Y, wherein range X is greater than range Y. This may allow for smother operation of the combined process.

The foregoing description of the present invention provides illustration and description, but is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The scope of the invention is defined by the claims and their equivalents.

The foregoing figures (FIG.) show particular unwinder systems used to feed elastomeric threads to a thread processing system. However, it should be understood that the present invention is not limited to the configuration of the unwinder systems shown. Alternative unwinder systems within the scope of the present invention may vary from the unwinder systems shown in a variety of ways not limited to but at least including: (1) the number of threads being fed; (2) types of packages supported; (3) positioning and use of guide members; and (4) number and type of drive systems. In particular, the present invention is suitable for use with any unwinder system where it would be desirable to monitor and control the tension of elastomeric or other types of thread in order to minimize tension variations in the thread from being introduced into a thread processing system.

Further, the written description of exemplary embodiments discusses the applicability of the present invention for providing elastomeric thread to a thread processing system in the form of a diaper manufacturing system. In particular, the application is preferably directed at the task of supplying elastomeric thread to be used for the elastic band features present near the open end of the legs of the diaper. While the present invention is shown in a diaper manufacturing environment, such illustration is not intended to be limiting and is included for exemplary purposes only. It will be understood by those skilled in the art after reading the description that the present invention is equally suitable for use for any other manufacturing process that utilizes an elastomeric thread.

Further, though only a few exemplary embodiments of the present invention have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible in these embodiments (e.g. types of rack systems, guide systems, drive systems, and control systems; sizes, structures, shapes and proportions of the various elements and mounting arrangements; and use of materials in terms of combinations and shapes) without materially departing from the novel teachings and advantages of the present invention.

Furthermore, the order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may be made in the design, operating configuration and arrangement of the preferred and other exemplary embodiments without departing from the spirit of the inventions as expressed herein. 

1) A thread feeding system comprising: guide rolls configured to guide an elastomeric thread through a thread path of the thread feeding system; a driven elastomeric thread package holder; a variable-speed motor configured to drive the driven elastomeric thread package holder; a first tension sensor configured to determine the tension on the thread; and a first tension controller device configured to control a speed of the variable-speed motor. 2) The thread feeding system of claim 1, wherein the speed of the variable-speed motor is maintained within a first predetermined range of thread tension values by the tension controller device. 3) The thread feeding system of claim 1 further comprising guide rolls and a tension sensor, wherein a wrap angle of the thread around the tension sensor is in the range between 5 and 210 degrees. 4) The thread feeding system of claim 1, wherein the driven elastomeric thread package holder is adapted to contact a core of an elastomeric thread package. 5) The thread feeding system of claim 1, wherein the driven elastomeric thread package holder is adapted to contact a circumference of an elastomeric thread package. 6) The thread feeding system of claim 1 further comprising a plurality of driven fiber package holders. 7) The thread feeding system of claim 1 further comprising at least one guide located less than 0.5 meter from the driven package holder. 8) A method for controlling elastomeric thread tension in a thread feeding system for a manufacturing system, comprising measuring a thread tension of a moving elastomeric thread; determining whether the moving thread has a tension that is out of range relative to a predetermined tension value; controlling the speed of a driven elastomeric thread package holder; and delivering the thread to a desired location in the manufacturing system. 9) The method of claim 8, further comprising determining whether an average tension for the moving thread is out of range relative to the predetermined tension value for the thread. 10) The method of claim 8, further comprising setting an alarm when the thread tension is at a level indicating at least one of broken, not moving and thread out of range tension level. 11) The thread feeding system of claim 8 further comprising at least one guide located less than 0.50 meter from the driven package holder. 12) The method of claim 8, wherein the driven elastomeric thread package holder is adapted to contact a circumference of an elastomeric thread package. 13) The method of claim 8, wherein the driven elastomeric thread package holder is adapted to contact a core of an elastomeric thread package. 14) The method of claim 8 further comprising a plurality of driven fiber package holders. 15) The method of claim 11, wherein the elastomeric thread package is an as-spun elastomeric thread package. 16) A thread feeding system comprising: guide rolls configured to guide an elastomeric thread through a thread path of the thread feeding system; a driven elastomeric thread package holder; a variable-speed motor configured to drive the driven elastomeric thread package holder; at least one guide located less than 0.5 meter from the driven package holder; a first tension sensor configured to determine the tension on the thread; and a first tension controller device configured to control a speed of the variable-speed motor; wherein the speed of the variable-speed motor is adjusted to maintain the tension on the thread within a predetermined range of thread tension values. 17) The thread feeding system of claim 16 further comprising guide rolls and a tension sensor, wherein a wrap angle of the thread around the tension sensor is in the range between about 5 and about 210 degrees. 18) The thread feeding system of claim 16, wherein the driven elastomeric thread package holder is adapted to contact a core of an elastomeric thread package. 19) The thread feeding system of claim 16, wherein the driven elastomeric thread package holder is adapted to contact a circumference of an elastomeric thread package. 20) The thread feeding system of claim 16 further comprising a plurality of driven fiber package holders. 